Conventionally, a fuel cell including an anode electrode to which fuel as such as hydrogen is supplied, a cathode electrode to which oxidant gas such as air is supplied, and an electrolyte membrane which is sandwiched between these electrodes has been commonly known. During power generation of the fuel cell, a reaction takes place that produces protons and electrons from hydrogen molecules at the anode electrode (H2→2H++2e−). The protons produced at the anode electrode are moved to the cathode electrode through the electrolyte membrane. On the other hand, the electrons are moved to the cathode electrode through an external circuit. Then, at the cathode electrode, a reaction takes place that produces water from the protons, the electrons, and oxygen in air (4H++O2+4e−→2H2O).
As such a fuel cell, for example, Patent Literature 1 discloses using a spiral CNT at a cathode electrode. A plurality of spiral CNTs are provided on a surface of an electrolyte membrane. Each spiral axis is disposed vertical to the surface of the electrolyte membrane. Accordingly, during power generation of the fuel cell, a current can flow in the direction of the spiral axis. Thus, the spiral CNT can function like a coil to form a magnetic field at the center of each spiral CNT, and therefore paramagnetic oxygen molecules can be easily attracted.
Also, for example, Patent Literature 2 discloses two methods for manufacturing a fuel cell comprising inclining a linear CNT and transferring it onto a surface of an electrolyte membrane. The first method is as follows. Firstly, a plurality of linear CNTs are grown vertically on a surface of a silicon substrate. Next, electrode catalysts are carried on the linear CNTs. Then, an ionomer solution is applied onto the surfaces of the linear CNTs. Subsequently, the growing ends of the linear CNTs and the surface of the electrolyte membrane are positioned opposite to each other. By applying a predetermined pressure between the linear CNTs and the electrolyte membrane, an inclined angle of each linear CNT is adjusted to connect the growing ends of the linear CNTs and the surface of the electrolyte membrane. Finally, the silicon substrate is removed to transfer the linear CNTs.
The second method is basically the same as the first method. However, the second method is different from the first method in that a process for providing ionomers on the surfaces of the linear CNTs and a process for connecting the linear CNTs and the electrolyte membrane are replaced. In other words, processes before carrying the electrode catalysts on the liner CNTs in the second method are the same those in the first method. In the second method, the linear CNTs and the electrolyte membrane are connected after the electrode catalysts are carried on the linear CNTs. Subsequently, the ionomers are provided on the surfaces of the linear CNTs. Finally, the linear CNTs are transferred by removing the silicon substrate.